创建aclocal.m4文件

aclocal [options]

根据已经安装的宏，用户定义宏和acinclude.m4文件中的宏将configure.ac文件所需要的宏集中定义到文件 aclocal.m4中。aclocal是一个perl 脚本程序，它的定义是：“aclocal - create aclocal.m4 by scanning configure.ac”

GNU autoconf tool. Place m4 macro definitions needed by autoconf into a single file. The aclocal command first scans for macro definitions in m4 files in its default directory (/usr/share/aclocal on some systems) and in the file acinclude.m4. It next scans for macros used in the configure.in file. It generates an aclocal.m4 file that contains definitions of all m4 macros required by autoconf.

--acdir=dir    Look for macro files in directory dir instead of the default directory.
--help    Print help message, then exit.
-I dir    Additionally, search directory dir for m4 macro definitions.
--output=file    Save output to file instead of aclocal.m4.
--print-ac-dir    Print the name of the directory to be searched for m4 files, then exit.
--verbose    Print names of files being processed.
--version    Print version number, then exit.

user input files   optional input     process          output files
================   ==============     =======          ============

                    acinclude.m4 - - - - -.
                                          V
                                      .-------,
configure.ac ------------------------>|aclocal|
                 {user macro files} ->|       |------> aclocal.m4
                                      `-------'